Field of the Invention
The invention relates to a controller for a drive train of a motor vehicle. The drive train controller includes an engine controller for controlling variables affecting engine torque, a transmission controller for controlling shifting events of an automatic transmission, and an interface interconnecting the transmission controller and the engine controller for allowing constant communications between the transmission controller and the engine controller.
Conventional transmission and engine controllers reduce engine torque by varying the ignition angle. The object being to make smoother gear shifts resulting in a more comfortable ride and to reduce the stress on the transmission. Such an engine and transmission controller pair is described in German Patents Nos. 29 35 916 C2 and 29 34 477 C3. The object is achieved in standard automatic transmissions of the conventional kind which generally include a planetary gear sets. The transmission controller transmits a relative amount of torque reduction, in accordance with which the ignition angle of the engine is retarded.
A similar system is known from Non-Prosecuted, Published German Patent Disclosure No. 40 37 092 A1. To improve the control of the entire drive unit, computer systems of the transmission controller and the engine controller are connected to one another so that they constantly communicate, via interfaces. In this way, the transmission controller sends a percentage-wise torque demand to the engine controller in a cyclical time cadence, and on the basis of this the engine controller automatically influences the engine torque.
In another known drive train controller, the transmission controller transmits a signal by which the (uncorrected) engine torque, which is present at the input shaft of the transmission, should be proportionally varied to the engine controller. The uncorrected engine torque is known to the transmission controller, because the transmission controller either calculates it itself or receives it from the engine controller via a communication line. Such a system is described in European Patent Disclosure No. 0 518 855 B1. The transmission controller need not contain any engine-specific data in order to convert a torque reduction into an ignition intervention, or an intervention into the injection or the valve control. The conversion takes place in the engine controller. This considerably reduces the needed number of variant forms of the transmission controller.